The two girls looked from each other to the ocean. Each felt powerfully drawn to it. "Uh, wanna go for a swim?" Maggie asked, although she and Cassie were both already shucking off their clothes. "Sure" said Cassie, as the two naked girls trotted to the shoreline. The amulet dropped to the sand behind them, forgotten.
Without a thought both plunged in. The cold of the water felt somehow less intense. Rather, the water and being in it felt both delightful and natural, like this was the place they were meant to be. Maggie gave a powerful kick, and her two legs moved together as one. Cassie felt her skin below the waist change, as if an extra layer of protection had sprung into existence. She looked down, and noted that her underwater vision was much clearer than ever before. Somehow, she wasn't surprised to see that her scaly legs had joined together into a fish tail. She l;ooked over at Maggie, who was swimming underwater with grace and ease, aided by the gills that had appeared on the side of her neck. "We're mermaids" Cassie said wonderingly, and noticed that her voice now carried underwater. "I know!" Maggie shouted back exultingly.
Suddenly Maggie and Cassie felt the sea around them change. Sweeter, less acidic. No longer the junkyard and cesspool that humanity had made of the ocean. They knew they were on another world. They saw an older, larger mermaid, with a kindly lined face, dark skin and iridiscent green scales swim up to them.
"Welcome, new sisters! Welcome to a world where your love is honored rather than disdained!"